The development of monoclonal antibodies has made possible new diagnostic and therapeutic techniques. Monoclonal antibodies are highly specific and can be used, for example, as vehicles to deliver other substances to specific target sites in vivo. It has been suggested in the literature that diethylenetriaminepentaacetic acid (DTPA) can form stable metal complexes when attached to protein. Krejcarek et al., 77 Biochem. & Biophys. Res. Commun. 581 (1977). Imaging of target sites iv vivo with radiometal-DTPA conjugated polyclonal antibodies prepared according to the method of Krejcarek have also been reported. Khaw et al., 209 Science 295 (1980). Despite separation by gel chromatography and dialysis of free and chelated metal from the metal chelate conjugated polyclonal antibodies targeted for a myocardial infarct, the gamma camera images show that a high proportion of the radiometal localized in the liver.
There remains an obvious need for an effective method to prepare metal conjugated monoclonal antibodies which permit highly selective delivery of metals to predetermined sites in vivo.